What's the use of explicitly defining a destructor?

What's the use of explicitly defining a destructor? When an object goes out of scope, its default destructor is called and memory space referenced by the *this pointer is automatically deallocated, right? Then what's the need for explicitly defining a destructor?

Deallocating memory isn't the only reason why one should overload the default destructor. If your class needs to perform some specific task before it's destroyed, overloading the destructor will allow the object to do just that.